Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected.
What is a theory? Or, more broadly, what is a good way of addressing intellectual problems? This paper explores the tension central to the notion of an ‘actor’—‘network’ which is an intentionally oxymoronic term that combines—and elides the distinction between—structure and agency. It then notes that this tension has been lost as ‘actor‐network’ has been converted into a smooth and consistent ‘theory’ that has been (too) simply and easily displaced, criticised or applied. It recalls another term important to the actor‐network approach—that of translation—which is another term in tension, since (the play of words works best in the romance languages) to translate is to also betray (traductore, traditore). It is suggested that in social theory simplicity should not displace the complexities of tension. The chapter concludes by exploring a series of metaphors for grappling with tensions rather than wishing these away, and in particular considers the importance of topological complexity, and the notion of fractionality.
Like other organisms, insects must balance two properties of ionic iron, that of an essential nutrient and a potent toxin. Iron must be acquired to provide catalysis for oxidative metabolism, but it must be controlled to avoid destructive oxidative reactions. Insects have evolved distinctive forms of the serum iron transport protein, transferrin, and the storage protein, ferritin. These proteins may serve different functions in insects than they do in other organisms. A form of translational control of protein synthesis by iron in insects is similar to that of vertebrates. The Drosophila melanogaster genome contains many genes that may encode other proteins involved in iron metabolism.
LAW, JOHN H. (Harvard University, Cambridge, Mass.) AND RALPiH A. SPLEPECKY. Assay of poly-,B-hydroxybutyric acid. J. Bacteriol. 82:33-36. 1961-A convenient spectrophotometric assay of bacterial poly-,B-hydroxybutyric acid has been devised. Quantitative conversion of poly-,B-hydroxybutyric acid to crotonic acid by heating in concentrated sulfuric acid and determination of the ultraviolet absorption of the produce permits an accurate determination of this material in quantities down to 5,ug. This method has been used to follow the production of poly-f3-hydroxybutyric acid by Bacillus megaterium strain KM. Recent reports concerning the widespread occurrence of poly-/-hydroxybutyric acid (Forsyth,
The three-dimensional structure of an apolipoprotein isolated from the African migratory locust Locusta migratoria has been determined by X-ray analysis to a resolution of 2.5 A. The overall molecular architecture of this protein consists of five long alpha-helices connected by short loops. As predicted from amino acid sequence analyses, these helices are distinctly amphiphilic with the hydrophobic residues pointing in toward the interior of the protein and the hydrophilic side chains facing outward. The molecule falls into the general category of up-and-down alpha-helical bundles as previously observed, for example, in cytochrome c'. Although the structure shows the presence of five long amphiphilic alpha-helices, the alpha-helical moment and hydrophobicity of the entire molecule fall into the range found for normal globular proteins. Thus, in order for the amphiphilic helices to play a role in the binding of the protein to a lipid surface, there must be a structural reorganization of the protein which exposes the hydrophobic interior to the lipid surface. The three-dimensional motif of this apolipoprotein is compatible with a model in which the molecule binds to the lipid surface via a relatively nonpolar end and then spreads on the surface in such a way as to cause the hydrophobic side chains of the helices to come in contact with the lipid surface, the charged and polar residues to remain in contact with water, and the overall helical motif of the protein to be maintained.
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